1. Field of the Invention
This invention relates to PCM (pulse code modulated) apparatus and, in particular, to novel and highly-effective apparatus that is suitable for recording and/or reproducing a PCM audio signal and that provides aperture compensation.
2. Description of the Prior Art
When a PCM audio signal is reproduced by conventional recording and/or reproducing apparatus, the high-frequency portion of the reproduced sound deteriorates because of the holding operation of the D/A (digital-to-analog) converter employed. This is generally known as the so-called aperture effect. In other words, since it takes a certain length of time for the output voltage from the D/A converter to reach the correct value corresponding to the input digital signal, the waveform of the signal from the D/A converter is distorted, as explained below. Even if the reproduced digital signal is supplied to the D/A converter during a sampling period, it takes a certain length of time for the output of the D/A converter to become stabilized.
An aperture compensation circuit for compensating for the deterioration of the high-frequency portion of the reproduced signal is thus indispensable to the optimal functioning of a PCM audio reproducing system. However, the prior art does not provide such compensation in an optimal manner. In particular, in the prior art, a special circuit for effecting aperture compensation is employed. Because of the addition of this special circuit, the manufacturing cost of the PCM apparatus is higher than is desirable.